SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 7) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings per share
Net income as reported and available to common stockholders									$ 37,712	$ 37,656	$ 40,554
Weighted average common shares, basic									41,762,000	41,612,000	41,490,000
Dilutive common stock options (treasury method) (in shares)									10,000	26,000	42,000
Shares used for dilutive computation (in shares)									41,772,000	41,638,000	41,532,000
Earnings per share - basic (in dollars per share)									$ 0.90	$ 0.90	$ 0.98
Earnings per share - diluted (in dollars per share)	$ 0.04	$ 0.50	$ 0.29	$ 0.07	$ 0.11	$ 0.49	$ 0.25	$ 0.05	$ 0.90	$ 0.90	$ 0.98
Long-Term Incentive Plan
Stock-based awards included in earnings per share
Common stock options outstanding to purchase common shares (in shares)					65,000					65,000	125,500
Stock Appreciation Rights (SARs)
Stock-based awards included in earnings per share
Stock Appreciation Rights (SAR) outstanding	361,356				361,356				361,356	361,356	361,356